This invention relates generally to apparatus for rapidly dissipating the heat energy generated by a voice coil actuator that is used to control the positioning of a valve spool.
As evidenced by U.S. Pat. No. 5,460,201 to Borcea et al. and U.S. Pat. No. 5,076,537 to Mears, Jr., linear voice coil actuators have been used for some time in association with spool type valves to control the positioning of the valve spool. The voice coil actuator generally involves a tubular wire coil located within a magnetic flux field provided by a stationary magnet. Applying an electrical current to the coil produces a directional force that is proportional to the current input producing relative motion between the magnet and the coil. Typically, the magnet is stationarily mounted and the coil is suspended in a frame within the flux field so that the frame moves linearly when a current is applied to the coil. In a spool valve application, the coil frame is coupled to valve spool and the position of the spool controlled by regulating the amount of current applied to the coil and the direction of current flow. Voice coil actuators have reliable operating characteristics, are generally hysteresis free and provide a smooth motion that makes them ideally well suited for use in controlling the operation of a spool valve.
Voice coil actuators, however, tend to generate a good deal of heat, particularly when the valve is cycled frequently over a relatively extended period of time. When housed in a compact package, the heat can build up rapidly to a point where the coil is damaged, thus rendering the actuator inoperative. By the same token, any electrical components located in close proximity with an overheated actuator can also become dangerously overheated.
It is therefore a primary object of the current invention to improve the heat dissipating characteristics of voice coil activated spool type valves.
A further object of the present invention is to improve the operation of spool valves by use of a voice coil actuator.
Another object of the present invention is to mount a spool type valve, a voice coil actuator for positioning the valve spool and electrical control components associated with the actuator in a compact package so that the actuator coil and the electronic components are not damaged by heat generated by the coil.
Yet another object of the present invention is to extend the operating life of a voice coil operated spool type valve by improving the heat dissipation characteristics of the valve.
These and other objects of the present invention are attained by a voice coil activated spool valve that includes a housing having a first chamber that contains a valve sleeve and a valve spool mounted for reciprocal movement within the sleeve along the axis of the housing. The housing further contains a second chamber adjacent the first chamber. The second chamber contains a linear voice coil actuator having a stationary magnet and a movable coil frame that is connected to the valve spool so that the spool is positionable when a current is applied to the coil. A thermally conductive polymer is placed between the outer surfaces of the actuator assembly and adjacent surfaces of the housing so that heat energy generated by the coil is rapidly transferred to the housing and the surrounding ambient. A highly conductive ferrofluid is also placed in the flux region of the magnet so that internal heat stored in the core of the actuator is transferred rapidly to the outer surface of the actuator. Fins are placed along the outside of the housing to further aid in the dissipation of heat to the surrounding ambient.